In an exterior building material, an interior building material, and kitchen equipment etc., an austenitic stainless steel plate represented by SUS304 and SUS316, and a ferritic stainless steel plate represented by SUS430 are often used. When used for such purposes, the stainless steel plate is not only required to have washability in order to facilitate easy removal of various types of dirt that adhere during manufacturing of the product and construction, as well as various types of dirt and fingerprints that adhere at the time of daily use, but in order for the dirt, fingerprints, and handling flaws to be hardly visible, an anti-glare property is also considered to be important.
Furthermore, in the field of precision equipment and electronic device members, for example, high speed and high density are required for an HDD (hard disk drive). The materials used for HDD members such as a rotating member, an arm member, a case member, and a cover, for example, not only possess excellent corrosion resistance, but are managed strictly with regard to dirt, such as particles (adhesive particles) and outgas. In addition, in a washing process during the manufacture of HDD members, for example, after degreasing with hydrocarbon, careful washing, such as ultrasonic cleaning, is performed by using a fluorine-based cleaning solution, a weak alkali-based cleaning solution, and extra pure water. Furthermore, if necessary, by performing vapor washing and finally performing a rinsing process a plurality of times using extra pure water, not only particles, but also ionic materials are removed. In addition, even minute dirt present in the air during the washing process can become a source of contamination, and therefore, generally, washing is performed in a Class 5 or higher clean environment according to JIS B9920. It must be noted that Class 5 or higher according to JIS B9920 is an environment in which the number of 0.1 μm particles per 1 m2 of air is 100000 or less, the number of 0.2 μm particles is 23700 or less, the number of 0.3 μm particles is 10200 or less, the number of 0.5 μm particles is 3520 or less, the number of 1 μm particles is 832 or less, and the number of 5 μm particles is 29 or less.
For the HDD members manufactured through such a washing process, ordinary steel, aluminum alloy, and stainless steel etc., are used, which are often used when non-electrolytic Ni plating has been performed. A main purpose of performing non-electrolytic Ni plating is to impart corrosion resistance and improve washability; however, such HDD members are required to have not only corrosion resistance and washability, but also a matte-finish surface having an anti-glare property so that fingerprints and minute flaws are hardly visible.
PTL 1 describes a stainless laminated damping steel plate having excellent anti-contamination properties for precision equipment covers such as HDD case covers. Ina normal stainless steel plate, if annealing and acid pickling are performed, a Cr depleted layer generated by annealing near the grain boundary in the vicinity of the surface is scarfed preferentially by acid pickling, and a small groove (micro groove) is formed along the grain boundary. The microgroove becomes a cause of occurrence of outgas due to the retention of an oil content when acid pickling is insufficient. Furthermore, dust adheres easily onto the micro groove, due to which the washability declines. Thus, in PTL 1, in order to prevent the occurrence of the micro groove, bright annealing or non-oxidation annealing is performed as the finish annealing after cold rolling.
Furthermore, PTL 2 describes a stainless steel plate in which the number of pin holes exceeding 0.25 mm2 in size on the surface of a temper-rolled plate is decreased to 10 or less per 10 cm2 so as to make it difficult for the minute dust and dirt in the air to adhere. The steel plate is manufactured by combining mechanical polishing, reduction annealing, and temper rolling by using a water-soluble lubricant.
In addition, PTL 3 describes a stainless steel plate having excellent fouling resistance and corrosion resistance. In such a steel plate, the fouling resistance and corrosion resistance are improved by controlling the surface roughness by performing bright annealing after finish rolling by using a dull roller.
Furthermore, PTL 4 describes a stainless steel plate having excellent contamination resistance, washability, and anti-glare property. The steel plate is manufactured by performing a first temper rolling with a mirror-finished roller after the finish annealing, and then performing a second temper rolling by using a dull roller.